1. Field of the Invention
The present invention relates to a light-emitting device manufactured by using an element (light-emitting element) that emits light by applying a current between electrodes with a luminescent material therebetween, and more particularly, relates to a sealing structure in the light-emitting device.
2. Description of the Related Art
In recent years, thin and light displays using light-emitting elements have been actively developed. In order to manufacture a light-emitting element, a material that produces luminescence by applying a current is interposed between a pair of electrodes. Since the light-emitting element itself emits light unlike a liquid crystal, a light source such as a backlight is not necessary, and thus, the element itself is quite thin. Accordingly, the light-emitting element is quite advantageous when thin and light displays are manufactured.
However, one of the backgrounds to the fact that no practical application has been achieved in spite of having these great advantages is a problem of reliability. A light-emitting element using an organic material is often deteriorated due to moisture (water), and has the disadvantage that it is hard to obtain reliability for a long period of time. The light-emitting element deteriorated due to water causes decrease in luminance or emits no light any longer. This is considered to be a cause for a dark spot (black spot) or luminance degradation from the periphery of a light-emitting device (luminance degradation in which a light-emitting area gradually decreases from an edge portion of a display device, which is hereinafter referred to as “periphery deterioration”) in a light-emitting device using a light-emitting element, and various measures has been proposed in order to suppress this deterioration (for example, refer Patent Documents 1 and 2).
However, even if these measures are applied, sufficient reliability has not been obtained yet, and further improvement in reliability has been desired.
In addition, for a light-emitting device, it is often the case that an organic insulating film that can be formed by coating is used as an insulating film. This organic insulating film has properties that are quite favorable in applying to a light-emitting device, such as superiority in flatness and capability to reduce unevenness of the underlying layer.
Patent Document 1:
Japanese Patent Application Laid-Open No. 9-148066
Patent Document 2:
Japanese Patent Application Laid-Open No. 7-169567